The present invention relates to power plant gas turbine controls and more particularly to controls in which improved ignition reliability is achieved with fuel viscosity variations caused by ambient temperature variations.
In recent years, gas turbines have been designed for increasingly higher loading which requires higher fuel flows. Since a limit exists on the pressure to which fuel can be pumped, fixed orifice nozzles have been made larger to accommodate the higher fuel flows required at higher loads.
Gas turbine availability for power generation depends directly on ignition reliability and in turn it has been suffering in recent years as a result of the effect of variable fuel viscosity in turbines requiring increasingly larger fuel nozzle orifices. Successful ignition requires fuel flow or pressure to be scheduled fairly accurately, and the effect of fuel viscosity on fuel flow has become much more critical with the larger fuel nozzles. In addition, gas turbine life has been foreshortened by over temperatures caused by overfueling a lower viscosity fuel through the larger nozzles during ignition.